Photographic element containing a protective matte layer



4, 1970 B. L. J. BYERLY ET AL 3,523,022

PHOTQGRAPHIC ELEMENT CONTAINING A PROTECTIVE MATTE LAYER Filed May 24,1965 H YDROPH/L /6 LA YER CONTAINING DE SE NS/ 772 E D S/L l/ER HAL/DEO/LVER HAL/DE EMULSION R suPPORr 2 HYDROPH/L/C BACK COAT/N6 FIG.

\ -S/L VER HAL/DE EMULSION SUPPOR 7' HYDROPH/L/C BACK COAT/N6HYDROPH/L/C LAYER CONTAIN/N6 k DESENS/T/ZED SILVER HAL/DE SILVER HAL/0EEMULS/OA/S CONTAIN/N6 OOLOR FORMERS \APSUPPORT HYDROPH/L/C BACK COAT/N6BERNARD L. J BYERLEY PETER DAV/S GUY WW STEVENS ATTORNEYS United StatesPatent US. Cl. 9674 7 Claims ABSTRACT OF THE DISCLOSURE Photographicelements containing a desensitized silver halide matte layer resistdeterioration. Silver halide grains which are insensitive to visibleradiation and silver halide emulsions containing such grains are usefulin a matte layer.

This application relates to photographic elements and more particularlyto photographic elements having a protective silver halide emulsionmatte coating. It also relates to the preparation of silver halideemulsions of low sensitivity.

It is common to provide photographic silver halide films comprising asupport having a silver halide emulsion coated on one side and, on thereverse side, a hydrophilic coating, such as a gelatin coating, tofunction as an anticurl layer or which may contain an antihalationagent. When such films are stacked or wound on spool, for instance, thesilver halide emulsion layer sometimes deteriorates when it comes intocontact with the hydrophilic back coating. This deterioration isbelieved to be due to diffusion of ingredients between the hydrophilicback coating and the emulsion layer. It therefore appears desirable toprovide a coating which efiectively prevents this undesired diffusion.

One object of our invention is to provide photographic elements having asupport coated with a silver halide emulsion on one side and ahydrophilic back coating on the reverse side, with a layer whichinhibits diffusion of ingredients between the emulsion and thehydrophilic back coating when the emulsion and back coating arecontacted.

Another object of our invention is to provide photographic elementscomprising a support having a hydrophilic coating on one side and, onthe opposite side, gelatin silver halide emulsion layers capable offorming colour images overcoated with a protective diffusioninhibitinglayer.

A further object of our invention is to provide a method of preparingsilver halide emulsions of low sensitivity.

Other objects of our invention will appear herein.

We have found that in photographic elements having a support coated onone side with a light sensitive silver halide emulsion layer, and havinga hydrophilic coating on the reverse side, the tendency of substituentsto diffuse between the emulsion and the hydrophilic back coatings are incontact with one another may be retarded by providing a protective mattelayer, over the emulsion or the hydrophilic back layer, comprising ahydrophilic coating containing coarse grained silver halide which hassuch low sensitivity to radiation that it is not developed duringordinary exposure and development of the light sensitive silver halideemulsion. The protective coatings of our invention provide goodprotection against undesired diffusion of substituents between silverhalide emulsions and hydrophilic backing layers.

Where we refer in this specification to an emulsion as being insensitiveor of a low sensitivity to light, we

mean that the emulsion is in a condition in which it does not show theeffects of imagewise exposure in the finally desired image. It will beappreciated that in a negative process, the emulsion must not only beinsensitive to light but also unfogged, whereas in a reversal colourprocess, the emulsion must be fogged completely before imagewiseexposure, so that it is not responsive to the imagewise exposure butdevelops uniformly to silver in the first black-and-white development.The silver is removed in the usual bleach.

In a preferred embodiment of the invention, a photographic elementcapable of producing colour images comprising a support having coated onone side thereof separate overlying light sensitive silver halideemulsion layers, is overcoated with a hydrophilic layer containininglarge grained, insensitive silver halide, the other side of the supporthaving a hydrophilic coating. In accordance with this arrangement,diffusion of substituents between the hydrophilic back coating and thesensitive emulsions is effectively inhibited.

In accordance with one embodiment of our invention, we provide a methodof precipitating silver halide which features the addition during theprecipitation of a bismuth salt to ensure that the silver halide grainsprecipitated are insensitive.

It is advantageous that the precipitated silver halide grains be ofspherical shape (as herein defined) and this may be achieved either bypreparing silver halide emulsions by methods of the type described by R.W. Berriman, I. Phot. Sci., 12, 121-133, 1964, or by employing a 1.5mole percent iodobromide emulsion which has been prepared byprecipitating the silver halide grains in the presence of a thalliumsalt. Suitably, 0.5 gram of thallous nitrate is present per mole ofsilver halide produced.

Silver halide precipitated in accordance with the invention constitutesa highly useful matting agent for incorporation in the protective,diffusion-inhibiting overcoatings of the invention.

By spherical as employed in this specification, we mean that the silverhalide grains are not plate-like as in the majority of silver halideemulsions employed in photography, but have increased thickness so thatthey more nearly approach a spherical or cubic shape.

The protective coatings of the invention have a matte surface, andappear to inhibit by limiting the area of contact when an emulsion layeris placed in contact with a hydrophilic coating.

FIG. 1 shows a support having coated on one side a hydrophilic backcoating and on the reverse side a light sensitive gelatin silver halideemulsion overcoated with a hydrophilic layer containing insensitivesilver halide grains.

FIG. 2 shows a light sensitive silver halide emulsion coated on asupport, the reverse side of which carries a hydrophilic back coatingovercoated with another hydrophilic layer containing insensitive silverhalide FIG. 3 illustrates a colour photographic element comprising asupport having a hydrophilic back coating on one side and, on theopposite side, a plurality of layers containing light sensitive silverhalide salts and colour formers, and having coated thereover ahydrophilic layer containing insensitive silver halide.

Our invention will be further demonstrated in the following examples.Example 1 shows the preparation of silver halide grains useful inaccordance with the invention.

EXAMPLE 1 A neutral silver bromide emulsion was precepitated in theusual manner except that varying quantities of bismuth mtrate were addedduring the precipitation. It was found that 0.5 gram bismuth nitrate permole of silver halide greatly reduced light sensitivity; that theadditionof 1 gram bismuth nitrate per mole of silver provided a greaterreduction of light sensitivity, and that when 2 grams bismuth nitrateper mole of silver were employed, all detectable light sensitivity wassuppressed.

Photographic elements containing the protective overcoating of theinvention are described in Example 2.

EXAMPLE 2 A colour forming photographic element comprising a supporthaving a hydrophilic antihalation back coating on one side an on thereverse side a plurality of light sensitive layers containing silverhalide and substituents capable of forming colour images was providedwith a protective coating over the light sensitive layers. Theprotective coating consisted of gelatin and the spherical, completelyinsensitive silver bromide grains obtained in Example 1 at aconcentration of 0.08 to 1.0 gram silver bromide per square meter. Whenwound on a spool, it was found that the protective layer in accordancewith the invention eifectively prevented diffusion of substituentsbetween the light sensitive layers and the hydrophilic antihalation backcoating. However, when a colour element of the same composition, butwhich did not contain the protective layer in accordance with theinvention, was wound on a spool, diffusion of substituents between thelight sensitive layers and the hydrophilic antihalation coatingoccurred, resulting in deterioration of the emulsion.

EXAMPLE 3 Example 2 was repeated using insensitive silver chloridegrains instead of insensitive silver bromide grains. Similar resultswere obtained with the additional advantage that no shadowing of theblue-sensitive layer occurred.

The low sensitive silver halide grains utilized in the invention shouldhave a speed at least times less than the image recording emulsion.Silver halide grains of this type may be provided, for example, byemploying emulsions which are not digested, or by oxidizing the emulsionwith bromine (see Photographic Sensitivity, Lowe et al., London, 1951,pages 112-125,) or by precipitating silver halidegrains by mixing asoluble silver salt and a soluble halide, in the presence of variousdesensitizers, in particular a bismuth salt. Bismuth nitrate giveshighly useful results; other bismuth salts are operable. The preferredconcentration range is above 0.1 and most preferably from 0.5 to 4 gramsbismuth salt per mole of silver halide produced. Advantageously, athallium salt is added to the emulsion during precipitation to obtainsubstantially spherical instead of the usual tabular grains. Also usefulare emulsoins known as Burtons emulsions, described in WallsPhotographic Emulsions, 1929, pages 52-53. When a completely foggedinsensitive emulsion is required it may be prepared in known manner bydigesting a silver halide emulsion with certain sulphur compounds,ammonia and excess silver nitrate, alkaline formaline or thioureadioxide.

Preferably, the insensitive silver halide grains are dispersed ingelatin although other hydrophilic colloid binders, such as polyvinylalcohol, hydrolyzed polyvinyl acetate and all the colloid bindersreferred to in US. Pat. 3,039,873, col. 13, lines 40-67, may be employedif desired. Similarly, the hydrophilic back coatings of the inventionmay be composed of any of those colloids.

Advantageously, when protective layers are provided for colour materialsemploying blue sensitive layers responding to wavelengths between about4,000 and 4,800 A., the silver halide grains employed are silverchloride. It has been found that silver bromide and silver bromoiodidegrains are relatively opaque to radiation between 4,000 and 4,800 A.,whereas silver chloride grains transmit such radiation. The use ofsilver chloride in the overcoatings thus avoids shadowing which occursin the blue sensitive layer when silverbromide or silver bromoiodide isemployed in the protective layer.

In order to obtain effective results, the silver halide grainsincorporated in the protective layers of the in vention must besubstantially spherical and have a particle size of at least 0.5 micron,a particle size from 0.5 to about 5l0 microns being particularlysuitable. Grain sizes smaller than 0.5 micron are less effective inpreventing dilfusion. The concentration of silver halide grains in theprotective layer may be about 0.02 to 4.0 grams per square meter, andpreferably is about 0.08 to 1.0 gram per square meter.

The unfogged relatively insensitive silver halide emulsions employed inthe invention are removable in the fixing baths employed in processingexposed silver halide materials, so that these emulsions do notcontribute to the graininess of the images produced in the sensitiveemulsion layer, or to any light-scattering effect on subsequent viewing.

This invention is particularly applicable to motionpicture film. Whenthe invention is practiced with colour reversal film, the emulsion iscompletely fogged before irnagewise exposure to ensure completedevelopment of the insensitive silver halide layer in the first (blackand white) development. This can be ensured by excess sulphur digestion,digestion with ammonia and excess silver nitrate, or with alkalineformaline or thiourea dioxide.

The invention has been described in detail with particular' reference topreferred embodiments thereof but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

We claim:

1. A photographic element comprising a support having coated on one sidea hydrophilic layer and on the opposite side a gelatin light-sensitivesilver halide emulsion layer, and a protective matte layer over one ofsaid layers comprising a hydrophilic colloid containing silver halidegrains substantially insensitive to light during normal exposure anddevelopment of the light-sensitive silver halide emulsion, said silverhalide grains comprising a desensitizer and being substantiallyspherical in shape and having a mean diameter of at least 0.5 micron.

2. A photographic element according to claim 1, wherein the protectivecoating is applied over the silver halide emulsion.

3. A photographic element comprising a support having a hydrophilic backcoating and on the reverse side a plurality of light-sensitive silverhalide containing layers having incorporated therein substances capableof forming color images, and a protective matte coating over saidlight-sensitive layers comprising a hydrophilic colloid binder dispersedtherein substantially light-in-' sensitive silver halide grains, saidsilver halide grains comprising a desensitizer and being substantiallyspherical in shape and having a mean diameter of at least 0.5 micron.

4. A photographic element according to claim 3, wherein the silverhalide grains are silver chloride.

5. In a photographic element having a support coated with alight-sensitive silver halide emulsion and, on the opposite side, ahydrophilic layer, the improvement which comprises a protective mattecoating, over said light-sensitive silver halide emulsion, comprising ahydrophilic colloid having dispersed therein substantiallylight-sensitive silver halide grains, said silver halide grainscomprising a desensitizer and being substantially spherical in shape andhaving a mean diameter of at least 0.5 micron.

6. A photographic element as in claim 1 wherein said grains is a bismuthsalt.

7. A photographic element as in claim 1 wherein said desensitizer forsaid substantially insensitive silver halide grains is bismuth nitrate.

References Cited 6 OTHER REFERENCES Chem. Abstracts, vol. 59, 1963 (Izu.Inst. Fizikokhim, Bulgar. Akad. Nauk 2, pp. 219-28 (1962)), 4716d.

Chem. Abstracts, vol. 59, 1963 (Sci. Phot. Proc. Intern. 5 Coloq. Liege1959, pp. 144-51 (pub. 1962)), 3464c.

UNITED STATES PATENTS NORMAN G. TORCHIN, Primary Examiner

